Nitric acid oxidation of sulfated fatty materials



. Patented Sept. 2, 194'? \e I i e i :m'rmo non) cinnamon or summer) rn'r'ry mn'rnnmns' 1 Francis J. Sprules, Arlington, and Richard Grif- A fith, Fair Haven, N. 3., designers to Nopco ghemlcal Company, a corporation of New ersey No Drawing. Application duly 6, i944,

, Seriai N0. 543335 5 Gialma. (11260-406) rrica The present invention relates to the nitric subsequently oxidized in the, presence of a catacid oxidation of sulfated fatty materials. More Myst-pre a y e manganese c p particularly, the present invention relates to the 7 Other objects and advantages o the present nitric acid oxidation of unsaturated acids and/or invention will become apparent from the present derivatives thereof and particularly to fatty acid 5 pe fi end m esters which have been previously sulfated. n general, the sulfetien 0f t fatty eeids is In U. S. application Serial No. 415,086, filed carried out ,by t t the tty ac 0 a y October 15, 1941, now Patent No. 2,365,290. at al t 8% ul a 'a t /2 h granted December 19, 1944, a method for th to an hour and thereafter washing the reaction oxidative scission of unsaturated fatty acids is 10 m tu with cold t solution t remove the disclosed. More particularly, the aforementioned xc The qu us layer is then sep r ted nd application discloses a method for oxidizing an the fatty lay Oxidized with nitric acid s p unsaturated fatty acid such as oleic acid so as to ticul'arly s t f th e n terproduce therefrom mono and dicarboxylic acids t h n discovered t h yi l f s i generally corresponding in length to the length 81011 pr are to some t t dependent of the chain on each side of the double bond. th ext nt f sulfati n n ral. the yi lds Preferably, as pointed out in the above applicaof scission products are h e w e e e s o tion, the catalyst used is a manganese compound the fatty ac ds a us d th r t an the fat y which provides greater yields than any of the acids themselves. Preferably, these esters are catalysts previously known in the art, the lower aliphatic esters such as the methyl As pointed out in the aforementioned applicaand ethyl este s of th f tty acids, but Other tion, greater yields are obtained when hydroxy esters may be used and preferably the lower acids are utilized rather than the original una pha ic est s, $0 10118 as t e presence o t saturated acid. Thus, for example, yields in p atic oup'does not give rise to a solid or, excess of 60% of the dibasic acid are produced i h y Viscous eOmPOU-Hd which it would be when the unsaturated acid itself is used and e t t0 S fat yields in excess of 70 or 80% of the theoretical After the sulfated product is prepared, t e are produced when hydroxylated fatty materials c a yst and n c de added. usually While are reacted. Asmay be understood, hydroxylated stirring and over a substantial period of time. materials must be ordinarily prepared from the Preferably, the nitric acid should be added exoriginal unsaturated acid by various methods tremely slowly, at least during an initial inducand even though the yields are higher, this is tion period. The mixture is then heated to a offset by the relatively complicated method necestemperature between 25 and 110 C. and prefersarily followed in initially preparing the hyably between 90 and 110 C. 4 This temperature droxylated fatty material. is preferably maintained forfrom 2-12 hours,

It has nowbeen discovered that yields corafter which the reaction mass may be cooled or responding to those derived from the hydroxsteam may be blown in and distillation of the ylated fatty materials and substantially in excess monocarboxylic acids started. The steam distilof those derived by oxidative scission of the lation is carried on until no more monocarboxylic' v original unsaturated acid may be prepared if 40 acids are driven ofi.- Thereafter, the monobasic sulfated fatty acids are subjected to oxidation. acid may be purified by extracting the same from This is all the more surprising since ordinarily the steam distillate with a suitable solvent such it would not be expected that sulfated fatty acids as hot dry ethylene dichloride. Other suitable would be quantitatively hydroylzed in situ and solvents such as benzene, chloroform, ether, etc. then oxidized by means of nitric acid to produce may also be used. the mono and dibasic scission products. The residue from the steam distillation is ad- It is one of the objects of the present invenjusted to a pH between 7 and 8 with causticsoda I tion, therefore, to provide a simple and ecoor other suitable base, and the aqueous layer nomical'process for the preparation of oxidative produced is removed and treated with dilute scission products of unsaturated fatty materials. sulfuric acid until it i acid to methyl orange A second object of the .present invention is (pH less than 4). It is then cooled to approxito provide an improved process for oxidizing mately 0 C. or any other suitable temperature to unsaturated fatty residues such as fatty acids quantitatively precipitate dicarboxylic acids and and/or esters thereof, whereby unsaturated fatty the precipitated dicarboxylic acids then filtered. acidsand/or esters thereof are sulfated and are The dibasic acids may also be recovered from the steam distillation residue by any other suitable process such as a selective solvent extraction process. For instance, the residue may be extracted first with a nonpoiar, or relatively slightly polar solvent such as a petroleum fraction to remove the unreacted oil and by-products without dissolving the dibasic acids. Thereafter, the residue may be extracted with a relatively more highly polar solvent, such as ethyl acetate..to dissolve the dibasic acids. Upon evaporation of the polar solvent extraction solution. the dibasic acids are left as a technically pure product. This product may be further refined and purified by recrystallization or other means.

A petroleum fraction was cited above as a suitable non-polar solvent; however, ethylene dichloride, chloroform, cold benzene, cold ether and other solvents of like character may be employed. Ethyl acetate was cited as a suitable relatively highly polar solvent; however, butanol.

hot water, hot methanol, hot ethanol, hot ether or the like may be substituted therefor.

The dicarboxylic acid and monocarboxyllc acids may also be separated by other means than steam distillation. Thus the oxidized mass may be treated and extracted with caustic soda solution to form the relatively soluble monosodium salt of the dicarboxylic acid. The residue may then be distilled to purify the monocarbcxylic acid. Preferably, an amount of approximately 3% of catalyst is used in the above reaction, although from A to 5% may be used with relatively good results. It is to be noted that the amount of catalyst is not critical and quantities greater than 5% may be employed. The amount of nitric acid employed should be somewhat greater than the amount theoretically required to cut the fatty chains and oxidize the carbon atoms at the point of scission to carboxyl groups, 1. e. greater than 4 mols per moi of fatty material.

The strength of nitric acid employed should be greater than about 60% and should preferably be commercial concentrated nitric acid having a strength between about 65% and about 71%, al-

though fuming nitric acid may be employed. In general, the preferred catalyst for the present oxidation reaction is a manganese compound which may be selected from the group consisting of a manganous or manganic salt or manganese oxide or any salt of a manganese-containingacid radicie. Examples of suitable manganese compounds coming within these requirements are the manganese oxides and manganese salts of which manganese chloride, manganese nitrate, manganese oxide, manganic oxide, manganese trioxide, manganese heptoxide, potassium permanganate, sodium manganite, manganese stearate, etc., may all be particularly mentioned. However, other oxidation catalysts have been found suitable, although the yields are not as great as those produced by the use of the manganese catalyst. Thus, nickel compounds and vanadium compounds are suitable and compounds of other metalshaving similar characteristics such aschromium, cobalt, iron, and copper. Compounds of other catalytic metals such as molybdenu'm, rhodium, palladium, silver, tantalum, tungsten, iridium, platinum, and gold may be used. These metals are all characterizedby having at least 2 incomplete outer electronic orbits in the atomic state. They are the metals of group 112 or groups V, V1 VII, and VIII in the socalled long series of the periodic table of Mendeleef.

Typical compounds of these metals of use in 4 this connection are the soaps, oxides, and salts, such as the halides. sulfates, nitrates. phosphates, etc. Other compounds such as the chromates, dichromates, vandadates, permanganates, manganates, manganites and molybdenates in which the metal is a constituent of the anion are suitable. Other complex salts such as the chloroplatinates, aurichiorides, etc. arealso useful in this connection.

The present invention is applicable to any of the fatty acids or fatty acid derivatives hav-' ing an unsaturated bond or its equivalent. Thus, oils, fats, fatty acids, or fatty esters containing fatty chains having unsaturated groupings intermediate the end of such chains are suitable (although preferably, the present processis practiced with esters of such fatty acids). Examples of suitable unsaturated acids are oleic acid, brassidic acid, erucic acid, linoleic acid, eleostearic acid, linolenic acid, clupanodonic acid, and esters thereof such as methyl oleate, ethyl oleate, methyl palmitoleate, etc. Instead of the pure acids, mixed acids may be employed which may be derived from the naturally occurring fats and oils, as, for example, eastor oil, olive oil, sardine oil and the like.

I The following examples serve to illustrate but are not intended to limit the invention.

Example I 50 grams of methyl oleate were sulfated for 20 minutes at a temperature of from 0-5 C. with 30 grams of 98% sulfuric acid. The sulfated mass was then stirred for half an hour, poured into 120 cc. of a water and ice mixture containing 20 grams of sodium chloride and the aqueous layer allowed to separate and drawn off. The aqueous layer was removed and the fatty layer heated to C. with 1 gram of manganese dioxide. 140 cc. (200 grams) of concentrated nitric acid were then run in with stirring over a period of 6 hours. The mixture was then heated further for 6 hours at l15-120 0. (oil bath temperature) and then distilled with stirring while 200 cc. of water in the form of steam were slowly added. The steam distillate was saturated with sodium chloride, ether extracted and dried. Removal of the ether from the extract left 11.5 grams of pelargonic acid. The residue from the steam distillation was then made alkaline with sodium hydroxide to a pH of 7-8, benzene extracted and the aqueous layer acidified with hydrochloric acid to a pH of somewhat less than 4. White solids precipitated which were filtered ofl and dried at 60 C. for 12 hours. The solid acid thus produced weighed 24 grams and had a neutral equivalent of 109 and corresponded to a yield of 76% of azelaic acid.

Example II 50 grams oieic acid were cooled to 0-8" and 30 grams 98% sulfuric acid added at that temperature as rapidly as possible with stirring. After A hour stirring, the mass was diluted with grams of ice water containing 20 grams NaCl, thoroughly mixed, and when the layers had separated, the aqueous wash waters were drawn off. The fatty layer, with 1 gram M1102 added thereto, was heated to 110 and a total of cc. by volume or 200 grams by weight HNO: (d=1.42) added with stirring. About 6 the total volume of HNOa was added rapidly at first. The addition of acid was then stopped during a brief induction period of about /2 hour. When brown fumes began to evolve and foaming started, carein! addition of the rest of the acid was made.

Approximately 6 hours total time was required for addition of HNOa. The reaction mixture was then refluxed with stirring for 4 hours more and steam distilled directly until no more monocarborwlic acids were driven 0!.

The steam distillate was treated with salt and extracted with dry ethylene dichloride. Removal of ethylene dichloride left 12 grams of pelargonic acid.

The residue from steam distillation was adjusted to pH 7-8 with 23.5% NaOH and the layers allowed to separate. The aqueous layer was then removed, made acid to methyl orange with dilute H2804 cooled to 0 C. and filtered. Air drying of the cake yielded 22 grams azelaic acid, neutral equivalent 106 or 73% of theory.

Having described our invention, what we claim as new and desire to be secured by Letters Patent is:

l. A process for oxidizing unsaturated fatty residues comprising sulfating said residues. treating the sulfated residue with nitric acid in the presence of an oxidation catalyst-and separating the mono and dicarhoxylic acids produced.

2. A process for oxidizing unsaturated fatty residues comprising sulfating said residues. treatin: the suifated residue with nitric acid in the presence of a manganese compound selected from the group consisting of manganese oxides and manganese salts and separating the mono and dicarboxylic acids produced.

3. A process for oxidizing methyl esters of unsaturated fatty acids to produce mono and dicarboxylic acids comprising suliating said methyl ester and then treating the Sulfated methyl ester with nitric acid in the presence of an oxidation catalyst.

4. A process for oxidizing unsaturated fatty acid esters comprising suifating said fatty acid esters, treating the sulfated fatty acid ester with nitric acid in the presence of an oxidation catalyst and separating the moncand dicarboxylic acids produced.

5. A process for oxidizing unsaturated fatty acid esters comprising sulfatmg said fatty acid ester, treating the sulfated fatty acid ester with nitric acid in the presence of a manganese compound selected from the group consisting of manganese oxides and manganese salts and sep arating the mono and vdicarhoxylic acids produced.

FRANCIS J. SPRUIES. RICHARD GRIFI'TI'E Number Name 2,365,290 Price Dec. 19, 1944 2,367,050 Price Jan. 9, 1945 

